1. Field of the Invention
The present invention relates to object detection devices, e.g., for use in ultrasonic-based object detection systems in the automotive sector.
2. Description of the Related Art
Normally, in driver assistance systems, parking assistance systems and proximity warning systems for motor vehicles, signals are actively transmitted into the surrounding area, in order to be able to detect objects within the surrounding area with the aid of the reflected waves. In addition to microwave-based systems, there are also ultrasonic-based sensors in which a transducer emits sonic waves, the sonic waves reflected from the surrounding area being measured. For example, a range, in which a reflecting object is situated with respect to the transducer, is then deduced in light of the propagation time.
The signal-to-noise ratio is to be regarded as a limiting factor for the performance of the object detection system, in particular, the operating range. However, especially precise processing requires expensive components and, in particular, high-resolution and, therefore, costly signal processing. In order to be able to isolate noise power from the signal line more effectively, parts of the received pulse, which are assumed not to contain a useful signal, are suppressed, for example. One known procedure is to suppress or set to zero a beginning portion of a received pulse, which corresponds to a certain minimum distance, e.g., 10 cm. In this manner, reflection components, which may come from external components of the vehicle itself, are suppressed. A further procedure is to use a threshold value and to suppress the signal, when it is less than the threshold value. Consequently, signal portions that do not contain any useful signal portions are suppressed during echo damping time periods, for example. In this connection, there are methods according to the related art, in which a threshold value predefined as constant is used, which is above a generally assumed noise level, and at or above which the signal is regarded as a signal that contains useful signal portions. However, this procedure for all-inclusive suppression of signal portions, which are regarded as control signals, results in limited performance.